Vehicle Seat

ABSTRACT

An adequate mechanical stiffness and strength are afforded to a tumble seat or a vehicle seat having a latch mechanism provided in a rear end of the seat cushion. A cushion frame (F 1 ) of the seat includes a side frame ( 5 ) extending in a fore and aft direction, and the side frame includes a first member ( 10 ) comprising a channel member having an open side facing sideways and a second member ( 11 ) attached to the first member so as to form a closed cross section jointly with the first member, and extending downward further than the first member. A latch mechanism is positioned under the first member and attached to the second member.

TECHNICAL FIELD

The present invention relates to a vehicle seat adapted to be mounted ona vehicle.

BACKGROUND ART

The tumble seat is known as a seat used for a second row or a third rowseat for a vehicle. The seat cushion of the tumble seat has a front endpivotally attached to the floor of the vehicle, and can be pivotedforward into an upright, retracted position with the seat back foldedonto the seat cushion. See JP2012-131248A, for instance. The rear end ofthe tumble seat is provided with a latch that can be detachably engagedby a striker fixedly secured to the floor. The latch can be manuallyreleased by using a lever connected to the latch via a cable.

The rear end of the tumble seat is secured to the seat solely via theengagement between the latch and the striker so that the latch isrequired to have an adequate mechanical stiffness and strength. Also,the structure of the latch is desired to be as simple as possible fromcommercial viewpoints.

BRIEF SUMMARY OF THE INVENTION

In view of such problems of the prior art, a primary object of thepresent invention is to provide an adequate mechanical stiffness andstrength to a tumble seat or a vehicle seat having a latch mechanismprovided in a rear end of the seat cushion.

A second object of the present invention is to provide a vehicle seat ofthis type which is simple in structure.

To achieve such objects, the present invention provides a vehicle seatincluding a seat cushion frame (F1) having a front part pivotallysupported by a floor and a rear part fitted with a latch mechanism (20)adapted to be detachably engaged by a striker (3) attached to the floor,wherein the seat cushion frame includes a pair of side frames (5)extending in a fore and aft direction on either side of the seat cushionframe, a front frame (6) connecting front ends of the side frames toeach other, and a rear frame (7) connecting rear ends of the side framesto each other, and at least one of the side frames includes a firstmember (10) comprising a channel member having an open side facingsideways and a second member (11) attached to the first member so as toform a closed cross section jointly with the first member, and extendingdownward further than the first member, the latch mechanism beingpositioned under the first member and attached to the second member.

According to this arrangement, as the second member of the side framewhich is required to support the latch mechanism forms a part of theclosed section, the latch mechanism can be attached to a highly stiffpart of the side frame. As the latch mechanism is positioned under thefirst member or under the closed cross section, the lateral dimension ofthe assembly including the latch mechanism and the side frame can beminimized. As the latch mechanism is attached to a part of the secondmember extending further downward than the first member, the mountingstructure of the latch mechanism can be simplified. As the latchmechanism can be attached to the second member from the lateraldirection, instead from below, the assembly work is simplified.

In this invention, the front frame may include a main part (6A)extending laterally and a pair of end parts (6B) each bent from acorresponding lateral end of the main part in a rearward direction andreceived in and fixedly secured to the corresponding first member.

According to this arrangement, a significant overlap may be createdbetween the front frame and the side frame so that the stiffness of thejoint between the first member and the front frame can be improved.

In this invention, the first member and the second member of each sideframe may jointly define a front opening (3) of the side member, and therear part of the corresponding end part of the front frame is passedinto a space defined jointly by the first member and the second memberfrom the front opening, the rear part being attached to both the firstmember and the second member.

According to this arrangement, as the end part of the front frame isconnected to both the first and second members, the stiffness of theside frame can be improved even further.

In a preferred embodiment of the present invention, each rear part ofthe front frame comprises a pipe member, and the second member isprovided with a contoured part (11C) conforming to an opposing curvedouter surface of the rear part.

The contoured part increases the stiffness of the second member so thatthe stiffness of the side member can be increased even further.

In a particularly preferred embodiment of the present invention, thefirst member comprises a vertically extending first side wall (10A), afirst upper wall (10B) extending from an upper edge of the first sidewall and a first lower wall (10C) extending from a lower edge of thefirst side wall in a same direction, and the second member (11)comprises a second upper wall (11B) overlying the first upper wall, anda second side wall (11A) extending downward from the second upper wallbeyond the first lower wall, wherein the first lower wall is providedwith a tab extending beyond a free end edge of the first upper wall, andthe second side wall is provided with a through hole for passing throughthe tab.

According to this arrangement, as the deformation of the first andsecond members are restricted by the tab being passed through thethrough hole, the stiffness of the side frame can be improved.

In this invention, a part of the tab projecting from the through holemay be provided with an engagement feature for engaging another member.

Thereby, the tab may be conveniently used for engaging or retaininganother member such as a control cable and a wire harness.

In this invention, the second side wall may be provided with areinforcement feature (15) extending from a part located above the firstlower wall to a part located under the first lower wall.

According to this arrangement, the stiffness of the second member can beincreased. In particular, the stiffness of the part of the second membersupporting the latch mechanism can be increased.

In a preferred embodiment of the present invention, a rear end of thefirst side wall is connected to a rear wall (10E) extending in a samedirection as the first side wall, and a rear end (11E) of the secondside wall is positioned ahead of the rear wall so that a rear opening(14) is defined in the side frame, a corresponding end of the rear framebeing fitted into the rear opening, and connected to both the firstmember and the second member.

Thus, the stiffness of the joint between the rear frame and the sideframe can be increased. As the rear frame is connected to both the firstmember and the second member, the stiffness of the side frame can beincreased.

In the present invention, the rear wall may connect the first upper walland the first lower wall to each other, and extend substantially flushwith a rear surface of the rear frame.

Thereby, the stiffness of the first member can be increased.

In the present invention, a connecting frame may be connected betweenlaterally middle parts of the front frame and the rear frame, theconnecting frame being formed with an engagement hole for engaging aretaining piece for retaining a cable.

The connecting member effectively increases the stiffness of the seatcushion frame. Also, the connecting frame may be used for securing aretaining member to the seat cushion frame.

Thus, according such arrangements, in a vehicle seat constructed as atumble seat, the mounting structure for mounting a latch mechanismconfigured to cooperate with a striker attached to a floor can berealized as a high stiff and simple structure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a seat frame of a vehicle seat of afirst embodiment of the present invention as seen from an upper leftdirection;

FIG. 2 is a fragmentary enlarged perspective view of a right seatcushion frame with a striker omitted from illustration;

FIG. 3 is a fragmentary side view as seen from a direction indicated byarrow III in FIG. 2;

FIG. 4 is a sectional view taken along line IV-IV of FIG. 3; and

FIG. 5 is an enlarged perspective view of a part of a seat framesurrounding a connecting frame as seen from a direction indicated byarrow V in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention in the form of a rear seat (whichmay be a second row or a third row seat) of a vehicle is described inthe following. In the following description, the directions are based onthe view of an occupant in the seat, and the central part of the seat isreferred to as being “inner” while the lateral end part is referred toas being “outer”. Various component parts are provided symmetrically toone another on either side of the seat, and may be denoted with samenumerals, but only one of each pair of such component parts may bediscussed in the following disclosure as they are mirror images of eachother.

As shown in FIGS. 1 and 2, the seat S includes a seat cushion S1incorporated with a seat cushion frame F1, and a pair of seat backs S2each incorporated with a seat back frame F2 pivotally connected to theseat cushion frame F1. The seat cushion frame F1 is pivotally supportedby a floor FL of the vehicle at a front end thereof via a pair ofsupport bases 2 fixedly attached to the floor FL, and detachably engagedby a pair of strikers 3 fixedly attached to the floor FL at a rear endthereof.

Each support base 2 projects upward from the floor FL, and has an upperend that pivotally supports the front end of the seat cushion frame F1around a rotational center line extending in the lateral direction. Eachsupport base 2 may be made of stamp formed sheet metal, and has an upperend projecting in a forward direction.

Each striker 3 is provided with a pair of side columns 3A extendingupward from the floor FL and a lateral beam 3B extending laterallybetween the upper ends of the side columns 3A. Each laterally outwardrear end part of the seat cushion frame F1 is fitted with a latch (whichwill be described hereinafter) which is detachably engaged by thelateral beam 3B of the corresponding striker 3.

The seat cushion S1 is formed by covering the seat cushion frame F1 witha pad and a skin member not shown in the drawings. Similarly, each seatback S2 is formed by covering the seat back frame F2 with a pad and askin member not shown in the drawings. The seat cushion frame F1 and theseat back frame F2 may be made of metallic sheet, pipe and/or rodmembers.

Each seat back frame F2 is connected to the seat cushion frame F1 via aper se known reclining mechanism R for adjustably fixing the seat backframe F2 at desired angular positions relative to the seat cushion frameF1. In particular, the reclining mechanism R is configured such thateach seat back S2 can be folded onto the upper surface of the seatcushion S1.

As shown in FIGS. 1 and 2, the seat cushion frame F1 is formed as arectangular frame including a pair of cushion side frames 5 extending inthe fore and aft direction along either side of the seat cushion frameF1, a front frame 6 extending between front parts of the cushion sideframes 5, a rear frame 7 extending between rear parts of the cushionside frames 5, and a connecting frame 8 connecting laterally middleparts of the front frame 6 and the rear frame 7 to each other. The frontframe 6 and the rear frame 7 are made of circular pipe members. Thefront frame 6 includes a laterally extending, linear main part 6A and apair of end parts 6B that are bent from respective ends of the main part6A in a rearward direction. The rear frame 7 extends linearly.

The two cushion side frames 5 are symmetric to each other (or mirrorimages of the other). As shown in FIGS. 2 to 4, the cushion side frame 5is formed by combining a first member 10 and a second member 11 whichare each made of stamp formed sheet metal. The second member 11 islocated on the inner side of the first member 10. The first member 10includes a first side wall 10A having a major plane facing the lateraldirection and extending in the fore and aft direction, a first upperwall 10B extending from the upper edge of the first side wall 10A in theinward direction, a first lower wall 10C extending from the lower edgeof the first side wall 10A in the inward direction, a first front wall10D extending from the front edge of the first side wall 10A in theinward direction, and a first rear wall 10E extending from the rear edgeof the first side wall 10A in the inward direction. Thus, as shown inFIG. 4, the first member 10 consists of a channel member having an openside facing the inward direction.

As shown in FIGS. 2 and 3, the front edge and the rear edge of the firstside wall 10A are each shaped in a semi-circular shape in side view sothat the first front wall 10D and the first rear wall 10E are curved ina corresponding manner as they extend vertically, and present convexsurfaces in the forward and rearward directions, respectively. The upperends of the first front wall 10D and the first rear wall 10E aresmoothly connected to the front end and the rear end of the first upperwall 10B, respectively, and the lower ends of the first front wall 10Dand the first rear wall 10E are smoothly connected to the front end andthe rear end of the first lower wall 10C, respectively. Thus, the firstupper wall 10B, the first lower wall 10C, the first front wall 10D andthe first rear wall 10E extend continuously along the periphery of thefirst side wall 10A.

As shown in FIGS. 2 to 4, the second member 11 includes a second sidewall 11A having a major place facing the lateral direction and extendingin the fore and aft direction, and a second upper wall 11B extendingfrom the upper edge of the second side wall 11A in the outwarddirection. The rear end of the second member 11 substantially align withthe rear end of the first member 10 in side view, but is shorter inlength than the first member 10. The first member 10 and the secondmember 11 are combined to each other so that the upper surface of thesecond upper wall 11B abuts the lower surface of the first upper wall10B, and the inner edge of the first lower wall 10C abuts the outersurface of the second side wall 11A, and are welded to each other atappropriate parts. As a result, the first member 10 and the secondmember 11 jointly define a rectangular pipe member 12 having asubstantially rectangular closed cross section. The second side wall 11Aextends downward further than the first side wall 10A.

The front end of the second side wall 11A is provided with a contouredpart 11C having a semi-cylindrical cross section and an inwardly facingconvex surface. The contoured part 11C extends forward beyond the frontend of the second upper wall 11B. The lower edge of the contoured part11C is bent in the outward direction so as to be laid over the lowersurface of the first lower wall 10C. The upper edge of the contouredpart 11C is spaced from the lower surface of the first upper wall 10B.Thus, the contoured part 11C and the corresponding part of the firstmember 10 jointly defines a C-shaped cross section, or a bore extendingin the fore and aft direction and having a front opening 13. The loweredge of the contoured part 11C is welded to appropriate parts of thefirst lower wall 10C. The second member 11 further includes a secondfront wall 11D that extends from the front edge of the second side wall11A in the outward direction, and is smoothly connected to the lower endof the contoured part 11C.

As shown in FIG. 3, the rear edge of the second side wall 11A is formedwith an arcuate cutout 11E which defines a circular rear opening 14 incooperation with the first rear wall 10E and the first upper wall 10B.The second member 11 is provided with a second rear wall 11F extendingoutward from a part of the rear edge of the second side wall 11A locatedunder the first lower wall 10C.

As shown in FIGS. 2 to 4, a tab 10F projects inward from the inner edgeof the first lower wall 10C, and a corresponding part of the second sidewall 11A is formed with a through hole 11G for passing through the tab10F. Thus, the tab 10F extends inward beyond the inner surface of thesecond side wall 11A. A free end part of the tab 10F is formed with anengagement hole 10G consisting of a through hole. The tab 10F receivedin the through hole 11G reinforces the first member 10 and the secondmember 11 against external force by reducing the relative movementbetween the first member 10 and the second member 11.

The second side wall 11A is provided with a pair of reinforcementfeatures 15 located ahead and behind the through hole 11G. In theillustrated embodiment, each reinforcement feature 15 consists of avertically extending bead formed by locally bulging the first side wall10A in the inward direction, and extends from a point located above thefirst lower wall 10C and a point located below the first lower wall 10C.Preferably, each reinforcement feature 15 extends substantially over theentire vertical extent of the second side wall 11A.

As shown in FIGS. 2 and 3, the end part 6B of the front frame 6 isplaced inside the channel cross section of the first member 10, andabuts the first side wall 10A, the first upper wall 10B and the firstlower wall 10C. The rear end of the end part 6B is fitted into the frontopening 13, and abuts the first side wall 10A, the first upper wall 10B,the first lower wall 10C and the contoured part 11C. The contoured parts11C is conformal to the outer surface of the end part 6B of the frontframe 6 so as to closely surround the outer surface of the end part 6B.The end part 6B of the front frame 6 is welded to the first member 10and the contoured part 11C at appropriate parts.

Each lateral end of the rear frame 7 is fitted into the correspondingrear opening 14, and abuts the inner surface of the first side wall 10Aat the end surface thereof. The outer circumferential surface of therear frame 7 abuts the first upper wall 10B, the first rear wall 10E,the first lower wall 10C, and the edge of the cutout 11E of the secondside wall 11A. The rear frame 7 is welded to the first upper wall 10B,the first rear wall 10E, the first lower wall 10C, and the second sidewall 11A at appropriate parts.

As shown in FIG. 2, each cushion side frame 5 is rotatably connected tothe corresponding support base 2 around a rotational center lineextending laterally. The pivot joint between a front end part of thefirst side wall 10A and the upper end of the support base 2 is coveredby a protective member 16 which is made by bending a metallic rod, andis welded to the front frame 6. The protective member 16 keeps the padof the seat cushion S1 and/or the fingers of the occupant away from thepivot joint between the first side wall 10A and the support base 2.

As shown in FIGS. 3 and 4, a latch mechanism 20 is attached to the outersurface of a part of the second side wall 11A extending further downwardthan the first lower wall 10C. The latch mechanism 20 includes a casing23 combining a base plate 21 and a cover plate 22 which are made ofstamp formed sheet metal, a hook 24 pivotally supported in the casing 23and a spring member 25 biasing the hook 24 in a prescribed direction.The base plate 21 and the cover plate 22 are provided with major planesopposing each other and facing the lateral direction. The cover plate 22is connected to the base plate 21 at the front and rear ends thereof,and a middle part (with respect to the fore and aft direction) thereofbulges outward away from the base plate 21 so that an inner space 26 isdefined between the cover plate 22 and the base plate 21. The lower edgeof the cover plate 22 is bent toward the base plate 21 so that the lowerend of the inner space 26 is substantially closed.

The lower ends of the base plate 21 and the cover plate 22 are formedwith vertically extending cutouts which are conformal to each other inside view so as to jointly define a slot 28 of the latch mechanism 20.The hook 24 is positioned in the inner space 26, and is pivotallysupported by the base plate 21 and the cover plate 22 via a pivot shaft24A provided in a vertically middle point of the hook 24 and extendingin the lateral direction. The hook 24 can be pivot between a lockposition where the hook 24 extends across the slot 28 and a releaseposition where the hook 24 is retracted away from the slot 28. Thespring member 25 in this case consists of a tension coil spring havingan end engaged by an engagement pin 24B attached to an upper end part ofthe hook 24 (on the side of the pivot shaft 24A remote from the mainpart of the hook 24) and another end engaged by the cover plate 22 so asto urge the hook 24 toward the lock position.

The latch mechanism 20 is positioned such that the base plate 21 abutsthe outer surface of a part of the second side wall 11A located underthe first lower wall 10C, and is attached to the second side wall 11A byfastening members 29 that integrally join the cover plate 22, the baseplate 21 and the second side wall 11A to one another. The fasteningmembers 29 may consist of threaded bolts and nut or rivets. The latchmechanism 20 is attached to the second side wall 11A at three locations,one in the front and two in the rear. In particular, a front part of thelatch mechanism 20 is attached to a part of the second side wall 11Alocated ahead of the front reinforcement feature 15, and the rear partof the latch mechanism 20 is attached to a part of the second side wall11A located behind the rear reinforcement feature 15. In the attachedcondition, the latch mechanism 20 is essentially located under the firstlower wall 10C, or, in other words, is located under the pipe member 12jointly formed by the first member 10 and the second member 11, anddefining a closed cross section. The slot 28 of the latch mechanism 20is located between the two reinforcement features 15 with respect to thefore and aft direction, and the upper end (bottom) of the slot 28 islocated under the lower edge of the second side wall 11A.

As shown in FIG. 3, in a normal use position of the seat S, the beam 3Bof the striker 3 abuts the upper end of the slot 28, and is retained inthis position by the hook 24 in the lock position. The lower end surfaceof the hook 24 is slanted in such a manner that when the beam 3B isforced into the slot 28, the hook 24 is displaced to the releaseposition against the biasing force of the spring member 25. Once thebeam 3B reaches the upper end of the slot 28, the hook 24 returns to thelock position under the biasing force of the spring member 25 with theresult that the beam 3B is firmly retained in the slot 28. If desired,the spring member 25 may be omitted, and the hook 24 may be normallybiased toward the lock position by using the gravitational force or anyother biasing means.

As shown in FIGS. 3 and 4, the engagement pin 24B of the hook 24 isconnected to an end of a control cable 32, and the other end of thecontrol cable 32 is connected to a lever 31 pivotally supported by therear frame 7. A strap (not shown in the drawings) is connected to thelever 31 so that the lever may be operated by a user via this strap.When this strap is pulled by the user, the hook 24 is displaced to therelease position via the lever 31 and the control cable 32 against thebiasing force of the spring member 25. Under this condition, the beam 3Bof the striker 3 may be removed from the slot 28.

As shown in FIG. 5, the connecting frame 8 consists of a rectangularpipe member extending in the fore and aft direction, and having arectangular cross section, and has a front end connected to a laterallymiddle point of the front frame 6 and a rear end connected to alaterally middle point of the rear frame 7. The connecting frame 8 isformed with a plurality of holes 8A passed through the side walls of theconnecting frame 8 and arranged along the fore and aft directions. Theseholes 8A are used for engaging retaining members (now shown in thedrawings) for retaining cable members such as a wire harness and acontrol cable. The retainer may consists of a clip made of plasticmaterial, and may be provided with resilient claws for snap fitting theclip into one or more of the holes 8A.

A rectangular support member 8B formed by bending a metallic rod isattached to the upper surface of the connecting frame 8 so as to extendhorizontally in both the lateral directions beyond the side profile ofthe connecting frame 8. A plurality of wavy wire springs 34 extendbetween the front frame 6 and the rear frame 7. The support member 8Band the wavy wire springs 34 jointly support the pad of the seat cushionS1 from below.

As shown in FIG. 1, a laterally middle part of the rear frame 7 isfitted with a support block 36 projecting upward from the rear frame 7.The upper end of the support block 36 supports a support shaft 37projecting from either lateral end of the support block 36. A supportplate 39 is fixedly attached to an outer surface of a rear end part ofthe first side wall 10A of the first member 10 such that the supportplate 39 projects upward from the first side wall 10A. The right seatback frame F2 is rotatably supported by the right support plate 39 viathe reclining mechanism R and by the support block 36 via the right endof the support shaft 37. The left seat back frame F2 is similarlysupported by the left support plate 39 and the left end of the supportshaft 37.

The seat back frame F2 consists of a substantially rectangular frameincluding a pipe frame 41 having a laterally extending main part and apair of end parts each bent from a corresponding end of the main partand extending downward. The seat back frame F2 further includes a pairof back side frames 42 each connected to the lower end of thecorresponding end part of the main part of the pipe frame 51, arectangular extension frame 43 connected to the main part of the pipeframe 41, and a pan frame 44 connected to the rear sides of the pipeframe 41 and the back side frames 42. The pipe frame 41, the side frames42, the extension frame 43 and the pan frame 44 all extend in a commonmajor plane. The right back side frame 42 is pivotally supported by thesupport plate 39 via the reclining mechanism R, and the left back sideframe 42 is pivotally supported by the right end of the support shaft37. The left seat back frame F2 is omitted from the description, as theleft seat back frame F2 is a mirror image of the right seat back frameF2, and is otherwise identical to the right seat back frame F2.

As discussed above, the latch mechanism 20 is positioned under therectangular pipe member 12 defining a closed cross section, and thesupport plate 39 and the support shaft 27 of the seat back frame F2 arelocated above the rectangular pipe member 12. In other words, the latchmechanism 20 is located under the support shaft 27 of the seat backframe F2.

How the seat S can be converted from the use position to the tumble(retracted) position is described in the following. First of all, byoperating the reclining mechanism R of the seat in the use position, theseat back S2 is folded onto the seat cushion S1. Then, the latchmechanism 20 is released by pulling the strap, and the seat S is broughtto the tumble position by lifting the rear end of the seat cushion S1 inan upward and a forward direction, thereby causing a rotation of theseat cushion S1 around the front end of the seat cushion S1.

The features and advantages of the illustrated embodiment are discussedin the following. The closed cross section jointly formed by the firstmember 10 and the second member 11 contributes to an increase in thestiffness of the cushion side frame 5. Thus, as the latch mechanism 20is mounted on the second member 11 which forms a part of this closedcross section, the stiffness of the structure for supporting the latchmechanism 20 can be maximized. As the latch mechanism 20 is positionedunder the first member 10 or under the closed cross section, the lateraldimension of the assembly including the latch mechanism 20 and thecushion side frame 5 can be minimized. As the latch mechanism 20 issecured to the part of the second member 11 projecting further downwardthan the first member 10 by using fastening member extending in thelateral direction, the mounting structure for the latch mechanism 20 canbe simplified. As the latch mechanism 20 can be attached to the secondmember 11 from a lateral direction, the assembly work is simplified, ascompared to the case where the latch mechanism 20 is attached in anupward direction.

As the base plate 21 and the second side wall 11A are laid over oneanother in the part where the latch mechanism 20 is attached to thesecond member 11, the stiffness of the latch mechanism 20 and the secondmember 11 can be increased.

As the end part 6B of the front frame 6 is positioned in a groovedefined by the first upper wall 10B, the first side wall 10A and thefirst lower wall 10C of the first member 10, and is connected to thefirst member 10 so as to be in contact with the first upper wall 10B,the first side wall 10A and the first lower wall 10C, the stiffness ofthe seat cushion frame F1 can be maximized. The rear end of the end part6B of the front frame 6 is fitted into the front opening 13 defined bythe first upper wall 10B, the first side wall 10A and the first lowerwall 10C of the first member 10, and is connected to the first member 10and the second member 11 with the end part 6B in contact with the firstupper wall 10B, the first side wall 10A, the first lower wall 10C andthe contoured part 11C, the stiffness of the seat cushion frame F1 canbe maximized.

The stiffness of the second member 11 is enhanced by the threedimensionally shaped, contoured part 11C and the reinforcement features15. As the reinforcement features 15 extend from a part of the secondmember 11 forming a part of the closed cross section to a part of thesecond member 11 at which the latch mechanism 20 is fastened to thesecond member 11, the load applied from the latch mechanism 20 to thesecond member 11 can be favorably transmitted to the part forming theclosed cross section.

As the lateral end of the rear frame 7 is fitted into the rear opening14 defined by the first member 10 and the second member 11, and isjoined to the closed cross section structure formed by the first member10 and the second member 11, the stiffness of the joint between thecushion side frame 5 and the rear frame 7 can be increased, and thestiffness of the cushion side frame 5 can be increased.

As the support plate 39 for pivotally supporting the seat back frame F2is attached to a part of the first member 10 forming the closed crosssection, the stiffness of the support plate 39 can be enhanced, and theseat back frame F2 can be supported in a stable manner.

As the front frame 6 and the rear frame 7 are connected to each othervia the connecting frame 8, the central opening of the rectangular seatcushion frame F1 is divided into two parts so that the stiffness of theseat cushion frame F1 can be increased. The connecting frame 8 may alsofunction as a support for the pad of the seat cushion, and may be usedfor engaging a member for retaining a control cable or any othercable-like members.

Although the present invention has been described in terms of apreferred embodiment thereof, it is obvious to a person skilled in theart that various alterations and modifications are possible withoutdeparting from the scope of the present invention. For instance, thesecond member 11 was positioned on the inner side of the first member 10in the illustrated embodiment, but the second member 11 may also bepositioned on the outer side of the first member 10 without departingfrom the spirit of the present invention.

1. A vehicle seat including a seat cushion frame having a front partpivotally supported by a floor and a rear part fitted with a latchmechanism adapted to be detachably engaged by a striker attached to thefloor, wherein the seat cushion frame includes a pair of side framesextending in a fore and aft direction on either side of the seat cushionframe, a front frame connecting front ends of the side frames to eachother, and a rear frame connecting rear ends of the side frames to eachother, and at least one of the side frames includes a first membercomprising a channel member having an open side facing sideways and asecond member attached to the first member so as to form a closed crosssection jointly with the first member, and extending downward furtherthan the first member, the latch mechanism being positioned under thefirst member and attached to the second member.
 2. The vehicle seataccording to claim 1, wherein the front frame includes a main partextending laterally and a pair of end parts each bent from acorresponding lateral end of the main part in a rearward direction andreceived in and fixedly secured to the corresponding first member. 3.The vehicle seat according to claim 2, wherein the first member and thesecond member of each side frame jointly define a front opening of theside member, and the rear part of the corresponding end part of thefront frame is passed into a space defined jointly by the first memberand the second member from the front opening, the rear part beingattached to both the first member and the second member.
 4. The vehicleseat according to claim 3, wherein each rear part of the front framecomprises a pipe member, and the second member is provided with acontoured part conforming to an opposing curved outer surface of therear part.
 5. The vehicle seat according to claim 1, wherein the firstmember comprises a vertically extending first side wall, a first upperwall extending from an upper edge of the first side wall and a firstlower wall extending from a lower edge of the first side wall in a samedirection, and the second member comprises a second upper wall overlyingthe first upper wall, and a second side wall extending downward from thesecond upper wall beyond the first lower wall, wherein the first lowerwall is provided with a tab extending beyond a free end edge of thefirst upper wall, and the second side wall is provided with a throughhole for passing through the tab.
 6. The vehicle seat according to claim5, wherein a part of the tab projecting from the through hole isprovided with an engagement feature for engaging another member.
 7. Thevehicle seat according to claim 5, wherein the second side wall isprovided with a reinforcement feature extending from a part locatedabove the first lower wall to a part located under the first lower wall.8. The vehicle seat according to claim 7, wherein a rear end of thefirst side wall is connected to a rear wall extending in a samedirection as the first side wall, and a rear end of the second side wallis positioned ahead of the rear wall so that a rear opening is definedin the side frame, a corresponding end of the rear frame being fittedinto the rear opening, and connected to both the first member and thesecond member.
 9. The vehicle seat according to claim 8, wherein therear wall connects the first upper wall and the first lower wall to eachother, and extends substantially flush with a rear surface of the rearframe.
 10. The vehicle seat according to claim 1, wherein a connectingframe is connected between laterally middle parts of the front frame andthe rear frame, the connecting frame being formed with an engagementhole for engaging a retaining piece for retaining a cable.